fog-explorer/libs/mission-logic/src/lib/encounter-resolver.ts

import {
  EncounterResult,
  MissionDifficulty,
  MissionState,
  ResolveEncounterInput,
  SurvivorStats
} from '@fog-explorer/api-interfaces';

import { applyPerkModifiers, clamp } from './perk-math';

const DIFFICULTY_BASE: Record<MissionDifficulty, number> = {
  [MissionDifficulty.Easy]: 0.72,
  [MissionDifficulty.Normal]: 0.6,
  [MissionDifficulty.Hard]: 0.48,
  [MissionDifficulty.Nightmare]: 0.38
};

export function resolveEncounter(input: ResolveEncounterInput): EncounterResult {
  const baseChance = DIFFICULTY_BASE[input.difficulty];
  const perkBoost = input.perkIds.length * 0.015;
  const statBoost =
    input.stats.stealth * 0.002 + input.stats.teamwork * 0.002 + input.stats.luck * 0.002;
  const successChance = clamp(
    applyPerkModifiers(baseChance + perkBoost + statBoost, []),
    0.05,
    0.95
  );
  const roll = seededRoll(input.seed ?? input.tickIndex);

  if (roll <= successChance) {
    return {
      outcome: 'success',
      text: 'The survivor outplayed the fog and advanced.',
      successChance,
      roll,
      nextState: MissionState.InProgress,
      nextStats: { ...input.stats, health: Math.min(100, input.stats.health + 1) }
    };
  }

  const injuryThreshold = successChance + 0.25;
  if (roll <= injuryThreshold) {
    const injured = applyDamage(input.stats, 14);
    return {
      outcome: 'injury',
      text: 'A close call leaves the survivor injured.',
      successChance,
      roll,
      nextState: injured.health <= 0 ? MissionState.Failed : MissionState.InProgress,
      nextStats: injured
    };
  }

  return {
    outcome: 'sacrifice',
    text: 'The fog claims another soul.',
    successChance,
    roll,
    nextState: MissionState.Failed,
    nextStats: { ...input.stats, health: 0 }
  };
}

function applyDamage(stats: SurvivorStats, amount: number): SurvivorStats {
  return {
    ...stats,
    health: Math.max(0, stats.health - amount)
  };
}

function seededRoll(seed: number): number {
  const normalized = Math.abs(Math.sin(seed * 99991)) * 10000;
  return normalized - Math.floor(normalized);
}